It is a common goal with vehicle manufacturers today to provide engine and combustion systems which improve fuel economy and, at the same time, reduce undesirable emissions. There are many systems which have been developed which accomplish one or more of these goals and achieve satisfactory results. Some of these systems include, for example, supplying prespecified amounts of fuel and air during certain engine operating conditions, various combustion chamber configurations including shaped bowls in the piston crown in order to secure desired air-fuel mixture and motion under various operating conditions, intake and exhaust valve mechanisms which create desired tumble and/or swirl patterns of in-cylinder flow motion, air-fuel mixture stratifications in the combustion chamber, and the like. Some of these systems are used in particular for direct injection spark ignited (DISI) engines.
Charge motion in the combustion chamber is an important factor for generating turbulence which in turn enhances the burn rate in engines. However, the tumble and/or swirl generation often comes at the expense of discharge coefficient, thus reducing the maximum power output of the engine.
Thus, there is a need for an engine combustion system which creates the desired turbulence in the combustion chamber and yet does not degrade the discharge coefficient.